Pump



R. S. ELBERTY PUMP June 18, 1946.

Filed Feb. 1, 1945 INVENTOR kofzerilillbenify Patented it"... is, .1946

I UNITED STATES PATENT OFFICE 1 My invention relates to a variable delivery Dump of the swash-plate type.

It is an object to provide a pump of the character indicated, which will produce a volume of flow in generally inverseproportion to the head.

- It. is another object to provide a pump of the character indicated. in which the flow is automaticaliy regulated in accordance with the disa tion I employ a swash-plate for actuating onev or more; pump pistons having suction and discharge valves associated therewith in the usual manner. Means, which I will term broadly a crank, is; employed to rock the swash-plate about its pivot so as to reciprocate the pistons. are so constructed and arranged that upon the attainment of a high head the pump strokes are automatically decreased so as to reduce the flow. The pump may also be arranged to reduce the flow as the head increases and after a definite head is attained to maintain a definite flow at the attained or a higher head. Such a pump has many uses, among others, in the machine tool industry.

'In the drawing which, shows, for illustrative purposes only, preferred forms of the invention- Fig. 1 is a vertical section through one form of my improved pump, the section being taken substantially in the plane of the broken line l--l of Fig. 2;

Fig. 2 is a bottom plan view of the lower or pump piston section of the pump shown in Fig. l

Fig. 3 is a fragmentary, sectional view illustrating a slightly modified form of adjustment means;

Fig. 4 is a fragmentary view of a. pump like that shown in Fig. 1 but illustrating a modification;

Figs. 5 and 6 are fragmentary sectional views illustrating still further modifications.

As illustrated, the body 5 of the pump is suitably supported as indicated at 8 and dips into an oil sump. The driving means for the pump in the form illustrated is an electric motor I and The pump parts i v 1, as by means of a coil spring 22 seating on a when such a motive means is employed the motor frame may be directly secured to the pump body 5 as by means of bolts. screws or the like 8. The pump body 5 in the form shown includes a bottom or cylinder block section having aplurality (in this case three) of cylinders 9. Each cylinder has a piston Ill. The bottom of the pump body is secured as by means of screws I2 to the cylindrical body 5 and the bottom plate isprovided with inlet valves l 3, one for each cylinder, as will ,be understood. The cylinder block or bottom of the pump body is provided with discharge valves l4, one for each cylinder, and the combined pump outlet 15 leads from the dis-- charge chamber into which all of the discharge valves empty.

The pistons l0 are operated by means of a v the shaft "is mounted for vertical movement preferably in needle bearings 2l-2I. The shaft 20 is urged in operative direction, that is, toward the swash-plate or downwardly. as viewed in Fig.

flange on a bearing cap 2! and at the upper end against an abutment plate 24, the position of Which',-and consequently the stress of the spring, may be adjusted as by means of an adjustment screw 25. Between the bearing cap 23 and the upper end of the shaft 20 I prefer to provide an anti-friction bearing of the so-called radial thrust type 28, all as will be understood.

The operation of the pump as 'thus for depast the discharge valve 14 into the discharge chamber and discharge pipe 15.

- Now, as the discharge pressure rises, the pistons meet increasing resistance, which tends to put ascents 3 increasing upward pressure on the shait'iili and tends to compress the spring 22 so as toshorten the piston strokes. In order to more accurately regulate thi upward movement of the shaft 28 and shortening of the piston strokes, I prefer to employ a stroke regulator which may consist of an annular plate 28 having a long bearing sleeve 2s slidable within the cylindrical pump body 5. This sleeve '29 preferably has a vertical slot 3t therein for the reception of a pin 3i so that the wobble plate doesnot rotate during its rocking motion. The stroke regulatin plate 28 is urged upwardly by a plurality (in this case three) of pistons 32 sli in cylinders 33 in the cylinder block. The space beneath the pistons 32 is connected to the discharge chamber by means of passages 3d. Thus, as the discharge head of the pump rises, the pressure'transmitted to the bottom ends of the pistons 32 will raise the stroke regulator plate 2d. This plate 28 is arranged to be contacted by one of the driving members, either the crank, roller iii. or the swash-plate itself, and in the form shown this plate is in position to be contacted by the swash-plate. Thus, when the plate 23 is raised, the swash-plate is slightly rocked about its central pivot i'i so as to shorten the stroke of each piston and the greater the discharge pressure of the pump the higher will the stroke regulator plate 28 be raised and the more will the strokes be shortened. Thus, at low head, when the plate 28 is in its lowermost position, the pump will pump maximum volume, but at low head. As the head increases, the strokes will be progressively shortened and, if

desired, the parts may be so proportioned that at any predetermined head the swash-plate will be so flattened in its position that there will be no further pumping action.

In the slight modification illustrated in Fig. 3,

I employ an adjustable stop screw 25' which may,

be positioned to contact the bearing cap 23 in any desired position of elevation. Thus, when the bearing cap 23 is in contact with the adjustable stop screw 25' there can be no further upward movement of the shaft to and consequently the pump will deliver a constant volume at the head attained at. the time of contact between the cap 23 and the 'stop screw 25', or at a higher head.

In the modification shown in Fig. 4, the pump parts may be substantially as heretofore described and the operation of pumping will be substan- However, in the modification shown in Fig. 4, the shaft 20' is preferably held tially the same.

against endwise movement and consequently there will be no raising Or lowering of the roller I! as in-the previous example. In the form of Fig. 4 the swash-plate i6 is mounted on a ball pivot 11 carried on a, stem extending through the upper wall 38 of the cylinder block and into the pump discharge chamber. Within the chamber the stem has an enlarged piston surface 538 and cylindrical skirt 8?, which fits in a bore 88111 the bottom block H. The space beneath the sleeve '8 is open to the sump through an opening 89. A spring so is interposed between the bottom of I the cylinder 88 and the piston member tit and constantly urges the piston member and conseluehtly the bail pivot il' upwardly. With the As the ball pivot ii is lowered, the swash-plate is flattened out and the stroke of each piston is of course reduced. There is thus no need of a stroke regulator such as the plate 23 of Fig, l, but I prefer to employ means such as the pin 3 i which may ride in a slot in the pump housing to prevent rotation of the swash-plate. I

, In the modification shown in Fig. 5, the swashplate is connected to each piston iii by means oi aspiring M. This spring is'securely connected to the swash-plate and to thepiston by any suitable means such as by grooving the piston and a lug on the swash-plate and snapping the spring into the grooves. Thus, upon the attainment of a high head in a pump as shown in the Fig. 5 modification, the spring M will be compressed and the pump stroke thus shortened so as to produce the results heretofore described in connection with the previous forms of the invention.

In the modification shown in Fig, fiinstead of connecting the spring 42 directly with the swashplate I connect the spring to the piston i6" and to a lug on a slide guide 43. The slide guide and swash-plate are connected by a short link dd having proper ball or other connections with those members. The actions of the forms shown in Figs. 5 and 6 are substantially the same. However, with the slide guide 43 present there is no tendency for the spring to cant nor to in anywise tend tobind the piston Iii.

Spring mounted pistons of the types shown in Figs. 5 and 6 are adaptable to pumps in general and may be actuated by means other than a swash-plate.

In all forms of the invention, therefore, I have provided means for automatically shortening the stroke and consequently reducing the volume at increased heads. As stated, the pump may be designed so as to cause the flow to cease entirely nected to said pistons for operating the latter, a

crank member for Operating the swash-plate member, spring means for normally urging one of the two last mentioned members in a direction, to produce maximum piston stroke, said spring means being yieldable to shorten the piston stroke when operating against a high head, means for adjusting the stress of said resilient means, and means independent of said pistons and actuated by the delivery pressure of said pump for shortening the piston strokes.

2. In a variable delivery pump of the charac ter indicated, a frame, a plurality of cylinders, pistons therein, a swash-plate for operating said pistons, means for operatlvely connecting said swash-plate and pistons. crank means for operating said swash-plate, spring neans iii-fixed lo cation on said frame for urgin the pivot of said swash piate and the crank relatively to each other in a direction to produce the maximum pis ton stroke, and means independent of said pistons a and actuable by the delivery ressure of the pump for acting on said spring means to move said pivot 3. In a variable delivery pump of the character indicated, a plurality of cylinders, pistons ter indicated, including a swash-plate and a crank for actuating the same, a plurality of cylinders, pistons in said cylinders and operatively connected to said swash-plate, and means independent of said pistons and actuated by the delivery pressure of the pump for moving the pivot of the I swash-plate and said crank away from each other,

for the purpose described. 5. In a variable delivery pump of the character indicated, including a shaft having a crank thereon, a plurality of cylinders, a swash-plate pivotally mounted at it center and positioned to be 0D- erated by said crank, pistons in said cylinders and operatively connected to said swash-plate, spring means for normally urging the pivot point of said swash-plate and said shaft relatively in a direction to produce maximum rocking motion of said swash-plate, and means independent of said pistons and actuated by the delivery pressure of the pump and acting against said resilient means to move the pivot point of said swash-plate and said shaft relatively in a direction to lessen the amplitude of rocking action of said swash-plate.

6. In a variable delivery pump of the character indicated, a plurality of cylinders, pistons therein, a swash-plate operatively connected to said pistons for actuating said pistons by said swash-plate, a shaft having a crank for operating said swash-plate, resilient means for urging said crank and shaft in a direction to produce maximum rocking of said swash-plate, and means independent of said pistons and movable by the delivery pressure of said pump for causing said shaft and crank to be moved relatively to the pivot point of said swash-plate for reducing the amplitude of rocking motion of said swash-plate.

7. In a variable delivery pump of the character indicated, a plurality of cylinders, a swash-plate,

a plurality of pistons in said cylinders and actuated by said swash-plate, a pivot member for said swash-plate, a crank for actuating said swashplate to rock the sameabout its pivot, resilient means for urging the pivot of the swash-plate in a direction to obtain maximum rocking motion of the swash-plate by said crank, and piston means operable by the delivery pressure of said pump and acting against said resilient means For moving the pivot 'point of said swash-plate in a direction to cause a reduction of the rocking ,motion of said swash-plate by said crank.

. ating the latter, means including a longitudinally 8. In a variable delivery pump of the character indicated, a plurality of cylinders, a plurality of pistons in said cylinders, a swash-plate for actuating the same, a crank for actuating the swashplate, said crank being mounted on a longitudinally movable shaft, spring means for urging said shaft in a direction to cause said crank to produce maximum rocking motion of said swashplate, regulating means including a member movable by the delivery pressure of the pump for 1imiting,m0ti0n of said shaft for lessening the rocking movement of said swash-plate by said crank,

9. In a variable delivery pump of the character indicated, a swash-plate member, a crank member, a stroke regulator cooperable with one of said members, pistons, cylinders for said pistons, said swash-plate being operatively connected to said pistons for operating the latter by said swash-plate, said stroke regulator including means independent of said pistons and actuable to cause said swash-plate to impart maximum strokes to said pistons, and means for adjusting the stress on said spring means.

11. In a variable delivery pump of the char-- acter indicated, a plurality of cylinders, a plurality of pistons in said cylinders. a swash-plate operatively connected to said pistons for actumovable shaft for actuating said swash-plate, spring means for urging said shaft in a direction to cause said swash-plate to impart maximum strokes to said pistons, control means independent of said pistons and actuated by the delivery pressure of the pump and acting against said spring means to cause said swash-plate to impart shorter strokes to said pistons, and means for limiting the action of said control means to limit the stroke shortening function thereof.

12. In a variable delivery pump of the character indicated, a plurality of cylinders, a 9111- rality of pistons in said cylinders, a swash-plate operatively connected to said pistons for actuating the latter, resilient means for causing said swash-plate to impart maximum strokes to said pistons, control means actuated by the delivery pressure of said pump and acting against said resilient means to cause said swash-plate to impart shorter strokes to said pistons, and stop means to limit the action of said control means. ROBERT S, ELBERTY. 

